transformation

1. Bacterial Transformation

2. Griffith’s experiment
Unlike conjugation and transduction where
physical contact is necessary for DNA transfer,
Transformation is a process, where a recipient
bacteria can directly take up a piece of DNA
from its surroundings.
Bacteria →uptake → DNA fragment (from its
surroundings)

3. • Unlike conjugation and transduction where
physical contact is necessary for DNA transfer,
Transformation is a process, where a recipient
bacteria can directly take up a piece of DNA
from its surroundings.
• Bacteria →uptake → DNA fragment (from its
surroundings)

4. From where DNA comes?
Bacteria lyse → release → DNA fragments
↓
‘Competent’ cell
↓
taken up
↓
integrate
↓
Chromosome

5. What is competent cell
• Normal bacterial cell is not permeable to DNA
fragments directly.
• It cannot pass through the membrane of
bacteria.
• But during the growth of bacterial cycle, i.e.
During exponential phase some bacteria shows
permeability means they can pass DNA through
their membrane.
• Such phase are called competent phase

7. Mechanism of transformation
Transformation: DNA in the environment of
a cell is taken into the recipient cell forming a
merozygote; then recombination occurs
• occurs naturally in some bacteria (e.g.,
Pneumococcus)
• occurs rarely in others, but can be promoted
by treating cells to destabilize their
membranes (e.g., in recombinant DNA work)
• can map genes by co-transformation
(frequency with which two genes are
simultaneously transferred

8. Mechanism of Transformation

9. Cotransfromation
• Genes located close
together are often
transferred as a unit to
recipient cell =
cotransformation
• Genes that are far apart
are less likely to be
transferred together
• Cotransformation is used
to map gene order

10. How do we get the plasmid inside of the
bacteria?
1. Obtain E. Coli
bacteria cells +
Add to CaCl2
(helps plasmid
attach to bacteria)
2. Add plasmid to
same microtube
1. E. Coli
2. pBlu
plasmid

11. How do we get the plasmid inside the
bacteria?
3. Heat shock: This
temporarily opens
pores to allow the
plasmid to enter the
bacteria…timing is
critical and very
important

12. Growing the bacteria
• After they have received
the plasmid
• Placed on a growth media
and allowed to grow.